1. Field of the Invention
The present invention relates to a shut-off device which closes automatically at a defined threshold temperature, with a shut-off element which is held in the open position by at least one element inhibiting a closing force.
2. Background Art
In order to limit damage in the event of a fire, plant, plant sections and pipeline systems which carry combustible gases or liquids are equipped with reliably isolating shut-off devices. Through the closing of the shut-off device the flow of medium is interrupted and the uncontrolled escape of combustible gases or liquids from a damaged plant section into the downstream system is prevented.
The DE-G 76 27 697 teaches an automatically closing shut-off valve, in particular for gas pipelines. Said shut-off valve exhibits a valve housing, a valve seat between gas inlet and gas outlet and a valve closing body. Said valve closing body is held in the open position by fixation with soft solder and can be moved into the closed position by means of a spring action. In the event of a fire, the soft solder softens and causes the automatic closing of the shut-off valve.
The disadvantage of such a shut-off system is that it can only be used on small valves of one particular kind (globe valves) so that it is limited in its scope of application mainly to the field of residential gas supplies. Furthermore, its function is restricted to the direct influence of temperature on the shut-off valve itself. Plant and plant sections which are operated at high pressure normally have so-called fire-protection valves which are located in a protected position outside the plant building at a sufficient safety distance from said building and can be closed either manually or by a mechanical drive in the event of a fire. It is often not possible to place such valves at a sufficient safety distance from the plant building due to local conditions or, in particular with small plant, the cost of location at a sufficient safety distance is not economically acceptable. Here in the event of fire the actuation of the valves is severely impaired or not possible.